The present invention relates generally to optical technology.
A circulator is often used with other optical devices to achieve certain optical functions. For example, a circulator can be used with a Brag Grating to extract an optical signal with a particular wavelength from a Wavelength Division Multiplexing (xe2x80x9cWDMxe2x80x9d) optical signal. FIG. 1 shows a four-port circulator 444 with four ports 1, 2, 3, and 4. An optical signal entering port 1 exits from port 2, while an optical signal entering port 2 exits from port 3, and an optical signal entering port 3 exits from port 4.
In one aspect, the invention provides an extendable four-port circulator. The extendable four-port circulator includes a middle birefringent crystal, a first birefringent crystal, a first non-reciprocal device, a second birefringent crystal, and a second non-reciprocal device. The first non-reciprocal device is coupled to the first birefringent crystal. The second non-reciprocal device is coupled to the second birefringent crystal. The middle birefringent crystal includes a first surface, a second surface, a third surface, and a fourth surface. The first surface is coupled to the first non-reciprocal device. The second surface is coupled to the second non-reciprocal device. The third surface defines a first and a second extension interface. The fourth surface defines a third and a fourth extension interface.
In another aspect, the invention provides a multi-port circulator. The multi-port circulator includes a middle birefringent crystal, a first common non-reciprocal device, a second common non-reciprocal device, a first common birefringent crystal, and a second common birefringent crystal. The first common non-reciprocal device is coupled to the middle birefringent crystal. The second common non-reciprocal device is coupled to the middle birefringent crystal. The first common birefringent crystal is coupled to the first common non-reciprocal device. The second common birefringent crystal is coupled to the second common non-reciprocal device.
In another aspect, the invention provides a multi-port circulator. The multi-port circulator includes a middle birefringent crystal, a first and a second common non-reciprocal device, a first and a third side birefringent crystal, and a second and a fourth side birefringent crystal. The first and the second common non-reciprocal devices each are coupled to the middle birefringent crystal. The first and the third side birefringent crystals each are coupled to the first common non-reciprocal device. The second and the fourth side birefringent crystals each are coupled to the second common non-reciprocal device.
In another aspect, the invention provides a multi-port circulator. The multi-port circulator includes a middle birefringent crystal, a first and a third non-reciprocal device, a second and a fourth non-reciprocal device, a first side birefringent crystal, a second side birefringent crystal, a third side birefringent crystal, and a fourth side birefringent crystal. The first and the third non-reciprocal devices each are coupled to the middle birefringent crystal. The second and the fourth non-reciprocal devices each are coupled to the middle birefringent crystal. The first side birefringent crystal is coupled to the first non-reciprocal device. The second side birefringent crystal is coupled to the second non-reciprocal device. The third side birefringent crystal is coupled to the third non-reciprocal device. The fourth side birefringent crystal is coupled to the fourth non-reciprocal device.
Aspects of the invention can include one or more of the following advantages. An extendable four-port circulator in an implementation of the instant invention may be cascaded to form a multi-port circulator. Other advantages will be readily apparent from the attached figures and the description below.